Calibration for Tandem PAIR of ATMS Instruments Using Lunar Observations

NOAA-20 is the follow on satellite program of SNPP operated by NOAA, and was sucessfully launched on Nov.18, 2017. The Advanced Technology Microwave Sounder (ATMS) onboard SNPP and NOAA-20 profiles atmospheric temperature and moisture in all-weather conditions, and supports continuing advances in numerical weather prediction (NWP) for improved short- to medium-range weather forecast skills. Since the ATMS onboard NOAA-20/SNPP are identical, it is critical to identify the calibration difference between these two instruments. Thus, a highly stable target with a well-known microwave radiation is required to evaluate the calibration consistency between the two ATMS instruments. This study develops a new vicarious calibration method based on lunar observations for on-orbit calibration evaluation of ATMS. Results show that with well-calibrated lunar observations, the calibration difference between NOAA-20 and SNPP can be well identified.